DESIGN FOR A BRAIN 



9/16 



In this section will be described some methods by which the 

 goal may be varied. Variations in the goal will be important in 

 those cases in which the goal is only a sub-goal, sought temporarily 

 or provisionally for the achievement of some other goal that is 

 permanent (S. 3/15). 



If the critical states' distribution in the main-variables' phase- 

 space is altered by any means whatever, the ultrastable system 

 will be altered in the goal it seeks. For the ultrastable system 

 will always develop a field which keeps the representative point 

 within the region of the critical states (S. 7/23). Thus if (Figure 

 9/16/1) for some reason the critical states moved to surround B 



JO- 



S' 



10 



2Q 



U 



Figure 9/16/1. 



instead of A, then the terminal field would change from one which 

 kept x between and 5 to one which kept x between 15 and 20. 

 A related method is illustrated by Figure 9/16/2. An ultra- 

 stable system U interacts with a variable A. 

 E and R represent the immediate effects which 

 U and A have on each other; they may be 

 thought of as C/'s effectors and receptors. If A 

 should have a marked effect on the ultrastable 

 system, the latter will, of course, develop a field 

 stabilising A ; at what value will depend markedly 

 on the action of R. Suppose, for instance, that 

 U has its critical states all at values and 10, so 

 that it always selects a field stabilising all its 

 main variables between these values. If R is such that, if A 

 has some value «, R transmits to U the value 5a — 20, then 

 it is easy to see that U will develop a field holding A within 

 one unit of the value 5; for if the field makes A go outside the 

 range 4 to 6, it will make U go outside the range to 10, and 



132 



Figure 9/16/2. 



